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authorDexuan Cui <decui@microsoft.com>2020-10-02 01:51:58 -0700
committerLorenzo Pieralisi <lorenzo.pieralisi@arm.com>2020-10-02 12:34:25 +0100
commit915cff7f38c5e4d47f187f8049245afc2cb3e503 (patch)
tree8eab40d7de565554779e91b9748f36ecdf31c0f0 /lib/test-kstrtox.c
parent9123e3a74ec7b934a4a099e98af6a61c2f80bbf5 (diff)
PCI: hv: Fix hibernation in case interrupts are not re-created
pci_restore_msi_state() directly writes the MSI/MSI-X related registers via MMIO. On a physical machine, this works perfectly; for a Linux VM running on a hypervisor, which typically enables IOMMU interrupt remapping, the hypervisor usually should trap and emulate the MMIO accesses in order to re-create the necessary interrupt remapping table entries in the IOMMU, otherwise the interrupts can not work in the VM after hibernation. Hyper-V is different from other hypervisors in that it does not trap and emulate the MMIO accesses, and instead it uses a para-virtualized method, which requires the VM to call hv_compose_msi_msg() to notify the hypervisor of the info that would be passed to the hypervisor in the case of the trap-and-emulate method. This is not an issue to a lot of PCI device drivers, which destroy and re-create the interrupts across hibernation, so hv_compose_msi_msg() is called automatically. However, some PCI device drivers (e.g. the in-tree GPU driver nouveau and the out-of-tree Nvidia proprietary GPU driver) do not destroy and re-create MSI/MSI-X interrupts across hibernation, so hv_pci_resume() has to call hv_compose_msi_msg(), otherwise the PCI device drivers can no longer receive interrupts after the VM resumes from hibernation. Hyper-V is also different in that chip->irq_unmask() may fail in a Linux VM running on Hyper-V (on a physical machine, chip->irq_unmask() can not fail because unmasking an MSI/MSI-X register just means an MMIO write): during hibernation, when a CPU is offlined, the kernel tries to move the interrupt to the remaining CPUs that haven't been offlined yet. In this case, hv_irq_unmask() -> hv_do_hypercall() always fails because the vmbus channel has been closed: here the early "return" in hv_irq_unmask() means the pci_msi_unmask_irq() is not called, i.e. the desc->masked remains "true", so later after hibernation, the MSI interrupt always remains masked, which is incorrect. Refer to cpu_disable_common() -> fixup_irqs() -> irq_migrate_all_off_this_cpu() -> migrate_one_irq(): static bool migrate_one_irq(struct irq_desc *desc) { ... if (maskchip && chip->irq_mask) chip->irq_mask(d); ... err = irq_do_set_affinity(d, affinity, false); ... if (maskchip && chip->irq_unmask) chip->irq_unmask(d); Fix the issue by calling pci_msi_unmask_irq() unconditionally in hv_irq_unmask(). Also suppress the error message for hibernation because the hypercall failure during hibernation does not matter (at this time all the devices have been frozen). Note: the correct affinity info is still updated into the irqdata data structure in migrate_one_irq() -> irq_do_set_affinity() -> hv_set_affinity(), so later when the VM resumes, hv_pci_restore_msi_state() is able to correctly restore the interrupt with the correct affinity. Link: https://lore.kernel.org/r/20201002085158.9168-1-decui@microsoft.com Fixes: ac82fc832708 ("PCI: hv: Add hibernation support") Signed-off-by: Dexuan Cui <decui@microsoft.com> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Reviewed-by: Jake Oshins <jakeo@microsoft.com>
Diffstat (limited to 'lib/test-kstrtox.c')
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